When to use Uber

2015-10-25

When should you use Uber rather than a regular taxi? Unless you’re some kind of
Randian monster, the answer is obviously more complicated than “whenever Uber
is cheaper”. But when is Uber cheaper than a cab?

The OpenStreetCab team then queried the Uber API to get the estimated price of
the same journeys if they had have been taken by UberX (Uber’s cheapest
service). The Uber API returns a price range, so they adopted the mean of the
upper and lower bound of these ranges as point estimates. Full details are
available in the OpenStreetCab paper. Here’s
what they found (Fig. 3 from their paper).

A better plot

It looks like Uber and yellow cabs cost about the same for rides below about
$35, but above that UberX is cheaper. But you could argue that the plot above
is a little misleading. Here’s a replot of the same data, which tells a
different story.

It’s now clear that Uber is more expensive below below $35 (the ratio of the
fares is greater than 1), and a lot more expensive for fares below $10.

The move away from the line of equal price for lower fares was all but
invisible on the original plot. This is because the data covers a large dynamic
range. This is a common visualization problem in many-orders-of-magnitude
sciences like astronomy. Often the solution is to switch to logarithmic scales.
But there’s a simpler approach that worked well here: plot the ratio of the two
values on one of the axes.

An even better plot?

In fact, you could still argue that the ratio plot above is misleading. Fig. 2
of the OpenStreetCab paper shows that the
median fare in the data is around $11, and fares over $30 make up a small
minority of journeys (around 15%, by eye). Both the original plot and my ratio
plot above therefore give undue emphasis to extremely rare expensive fares,
giving the false impression that Uber is cheaper half the time.

A smart way to fix this would be to use the width or color of the line to
indicate what fraction of rides occur at that price. This would give visual
weight to the region of the plot that matters for most of the people, most of
the time.

And a more rigorous analysis should take into account the uncertainties on the
OpenStreetCab data, which are due to the adopted Uber prices being based on the
intervals returned by their API.

But for now, here’s a quick and dirty solution: change the range of the
horizontal axis so that you see only the most typical fares.

To sum up: if all you care about is money then don’t use UberX. And, when
comparing two similar values over a large range, plot their ratio on one of the
axes.